Heretofore, cast practice aerial bombs have been produced from grey iron castings produced in a foundry employing sand molds and a conventional resin bonded core. In such production, an elongated generally teardrop shape body has been produced with an internal axial opening resulting from the presence of a core within the sand mold and followed by an extensive machining operation to produce the ultimate aerodynamic shape. In order to minimize voids in the casting operation as characteristic in foundries, it has been necessary to cast each bomb with significant riser or sprue extending upward out of the mold and then subsequently removing said riser or sprue by cutting or machining operation. Often the total volume of the cast metal in the sprue or riser approximates that of the cast body. This has resulted in the past in a necessary melting of far greater quantities of cast material than actually form a part of the finished product followed by reclamation of the sprue or riser.
In order to cast the actual opening rather than machining a substantial diameter hole, the use of a consumable core made up of resin bonded sand has been the practice, in the process of casting the resin bonded core means in the required space, until the metal hardens and is subsequently removed. At molding temperatures, the resin is vaporized and adds to the total air contamination. The need for melting and casting far greater volume than the finished product plus the vaporization of mold core binder results in unnecessary air pollution. Thereafter, the elimination of excess sand plus the necessary machining of the external plus the internal surfaces of the casting produces greater use of energy plus contamination as well.
Likewise, it has often been found towards the end of the steps of manufacturing of the cast molding, a soft spor or void appears in the cast metal resulting in a rejection.